1. Field of the Invention
This invention relates to an apparatus for displaying a fluorescence image, wherein a fluorescence image in accordance with characteristics of fluorescence, which is produced from a measuring site in a living body when the measuring site is exposed to excitation light, is displayed.
2. Description of the Related Art
There have heretofore been proposed apparatuses for displaying a fluorescence image, wherein location and an infiltration range of diseased tissues are displayed as an image by the utilization of characteristics such that, in cases where excitation light having wavelengths falling within an excitation wavelength range for an intrinsic dye in a living body is irradiated to the living body, a pattern of a fluorescence spectrum of fluorescence produced by the intrinsic dye in the living body varies for normal tissues and diseased tissues.
FIG. 12 shows typical fluorescence spectra of the fluorescence produced from normal tissues and the fluorescence produced from diseased tissues, which fluorescence spectra have been measured by the inventors. It is assumed that the thus produced fluorescence results from superposition of the fluorescence produced by various kinds of intrinsic dyes in the living body, such as FAD, collagen, fibronectin, and porphyrin.
With the proposed apparatuses for displaying a fluorescence image, basically, fluorescence components of the fluorescence, which has been produced from a measuring site in the living body when the excitation light is irradiated to the measuring site, are detected via each of a plurality of band-pass filters, and the fluorescence components having wavelengths falling within desired wavelength regions are thereby selected. Also, signal intensities of the thus selected fluorescence components are detected. Thereafter, information in accordance with the detected signal intensities is displayed as a fluorescence image on a monitor, or the like. Therefore, a person who sees the displayed information is capable of recognizing the state of the diseased tissues. In many cases, the apparatuses for displaying a fluorescence image take on the form built in endoscopes, which are inserted into the body cavities, colposcopes, operating microscopes, or the like.
Ordinarily, as a combination of wavelength regions of the fluorescence components to be selected from the fluorescence, a combination of a red wavelength region and a blue wavelength region, at which the difference between the pattern of the fluorescence spectrum obtained from normal tissues and the pattern of the fluorescence spectrum obtained from diseased tissues occurs markedly, or a combination of an entire measurement wavelength region, from which a large amount of light is capable of being obtained, and the blue wavelength region, or the like, has heretofore been selected. For example, in cases where the combination of the red wavelength region and the blue wavelength region is to be selected, a mosaic filter constituted of a combination of band-pass filters, which transmit only the fluorescence components having wavelengths falling within the red wavelength region, and band-pass filters, which transmit only the fluorescence components having wavelengths falling within the blue wavelength region, has heretofore been located at a front surface of an image sensor. In this manner, the fluorescence components having wavelengths falling within the red wavelength region and the fluorescence components having wavelengths falling within the blue wavelength region have heretofore been detected. In cases where the combination of the entire measurement wavelength region and the blue wavelength region is to be selected, a mosaic filter constituted of a combination of blank areas, which transmit the fluorescence components having wavelengths falling within the entire measurement wavelength region, and the band-pass filters, which transmit only the fluorescence components having wavelengths falling within the blue wavelength region, has heretofore been utilized.
However, the fluorescence, which is produced from the living body tissues when the living body tissues are exposed to the excitation light, is weak. With the conventional apparatuses for displaying a fluorescence image described above, the fluorescence components having wavelengths falling within a desired wavelength region are selected from the weak fluorescence by use of the band-pass filter, which transmits only the fluorescence components having wavelengths falling within a primary color wavelength region, such as the red wavelength region or the blue wavelength region. Therefore, the conventional apparatuses for displaying a fluorescence image described above have the problems in that the efficiency, with which the fluorescence is utilized, cannot be kept high, adverse effects of photon noise, and the like, are apt to occur during photoelectric conversion, and a signal-to-noise ratio of the fluorescence image cannot be kept high.
The primary object of the present invention is to provide an apparatus for displaying a fluorescence image, wherein an efficiency, with which fluorescence having been produced from a measuring site in a living body exposed to excitation light, is utilized, is enhanced, and a signal-to-noise ratio of a displayed fluorescence image is kept high.
Another object of the present invention is to provide an apparatus for displaying a fluorescence image, wherein a fluorescence image is capable of being displayed in a real time mode, and a reliability of the displayed fluorescence image is capable of being enhanced.
The present invention provides a first apparatus for displaying a fluorescence image, comprising:
i) excitation light irradiating means for irradiating excitation light to a measuring site in a living body, the excitation light causing the measuring site to produce fluorescence,
ii) image information acquiring means for acquiring image information in accordance with a signal intensity of fluorescence components of the fluorescence having been produced from the measuring site exposed to the excitation light, which fluorescence components have wavelengths falling within at least one desired wavelength region, and
iii) displaying means for displaying the acquired image information,
wherein the image information acquiring means comprises:
a) a complementary color filter for transmitting only fluorescence components of the fluorescence, which fluorescence components have wavelengths falling within a wavelength region acting as a complementary color with respect to the desired wavelength region,
b) complementary color signal intensity detecting means for detecting a signal intensity of the fluorescence components of the fluorescence, which fluorescence components have passed through the complementary color filter,
c) entire signal intensity detecting means for detecting a signal intensity of fluorescence components of the fluorescence, which fluorescence components have wavelengths falling within an entire measurement wavelength region of the fluorescence, and
d) signal intensity calculating means for calculating the signal intensity of the fluorescence components of the fluorescence, which fluorescence components have wavelengths falling within the desired wavelength region, from the signal intensity, which has been detected by the complementary color signal intensity detecting means, and the signal intensity, which has been detected by the entire signal intensity detecting means.
In the first apparatus for displaying a fluorescence image in accordance with the present invention, the entire signal intensity detecting means should preferably comprise an all-pass filter for transmitting the fluorescence components of the fluorescence, which fluorescence components have wavelengths falling within the entire measurement wavelength region of the fluorescence, and
entire measurement signal intensity detecting means for detecting the signal intensity of the fluorescence components of the fluorescence, which fluorescence components have passed through the all-pass filter.
In such cases, a plurality of complementary color filters and a plurality of all-pass filters should preferably be arrayed alternately on a two-dimensional plane so as to constitute a mosaic filter.
The present invention also provides a second apparatus for displaying a fluorescence image, comprising:
i) excitation light irradiating means for irradiating excitation light to a measuring site in a living body, the excitation light causing the measuring site to produce fluorescence,
ii) image information acquiring means for acquiring image information in accordance with a signal intensity of fluorescence components of the fluorescence having been produced from the measuring site exposed to the excitation light, which fluorescence components have wavelengths falling within at least one desired wavelength region selected from among a blue wavelength region, a green wavelength region, and a red wavelength region, and
iii) displaying means for displaying the acquired image information,
wherein the image information acquiring means comprises:
a) a yellow filter for transmitting only fluorescence components of the fluorescence, which fluorescence components have wavelengths falling within a yellow wavelength region acting as a complementary color with respect to the blue wavelength region,
b) a magenta filter for transmitting only fluorescence components of the fluorescence, which fluorescence components have wavelengths falling within a magenta wavelength region acting as a complementary color with respect to the green wavelength region,
c) a cyan filter for transmitting only fluorescence components of the fluorescence, which fluorescence components have wavelengths falling within a cyan wavelength region acting as a complementary color with respect to the red wavelength region,
d) complementary color signal intensity detecting means for detecting a signal intensity of the fluorescence components of the fluorescence, which fluorescence components have passed through the yellow filter, a signal intensity of the fluorescence components of the fluorescence, which fluorescence components have passed through the magenta filter, and a signal intensity of the fluorescence components of the fluorescence, which fluorescence components have passed through the cyan filter,
e) entire signal intensity calculating means for calculating a signal intensity of fluorescence components of the fluorescence, which fluorescence components have wavelengths falling within an entire measurement wavelength region of the fluorescence, from the signal intensity of the fluorescence components having wavelengths falling within the yellow wavelength region, the signal intensity of the fluorescence components having wavelengths falling within the magenta wavelength region, and the signal intensity of the fluorescence components having wavelengths falling within the cyan wavelength region, which signal intensities have been detected by the complementary color signal intensity detecting means, and
f) signal intensity calculating means for calculating the signal intensity of the fluorescence components of the fluorescence, which fluorescence components have wavelengths falling within the desired wavelength region, from the signal intensities, which have been detected by the complementary color signal intensity detecting means, and the signal intensity of the fluorescence components having wavelengths falling within the entire measurement wavelength region of the fluorescence, which signal intensity has been calculated by the entire signal intensity calculating means.
In the second apparatus for displaying a fluorescence image in accordance with the present invention, a plurality of yellow filters, a plurality of magenta filters, and a plurality of cyan filters should preferably be arrayed alternately on a two-dimensional plane so as to constitute a mosaic filter.
In the first and second apparatuses for displaying a fluorescence image in accordance with the present invention, the image information acquiring means may employ one of various techniques for acquiring the image information. For example, the image information acquiring means may employ a technique for acquiring the image information in accordance with the signal intensity of the fluorescence components of the fluorescence, which fluorescence components have wavelengths falling within only one desired wavelength region. Alternatively, the image information acquiring means may employ a technique for acquiring the image information in accordance with a ratio among the signal intensities of the fluorescence components of the fluorescence, which fluorescence components have wavelengths falling within a plurality of desired wavelength regions.
Also, in the first and second apparatuses for displaying a fluorescence image in accordance with the present invention, the displaying means may employ one of various displaying techniques. For example, in cases where the image information acquiring means acquires the image information in accordance with the ratio among the signal intensities of the fluorescence components of the fluorescence, which fluorescence components have wavelengths falling within the plurality of the desired wavelength regions, the ratio among the signal intensities may be displayed on a monitor, with a printer, or the like. Alternatively, a tint of a display color or luminance may be altered in accordance with the ratio among the signal intensities.
The term xe2x80x9call-pass filterxe2x80x9d as used herein also includes a blank area for transmitting the fluorescence components of the fluorescence, which fluorescence components have wavelengths falling within the entire wavelength region of the fluorescence.
With the first apparatus for displaying a fluorescence image in accordance with the present invention, the signal intensity of the fluorescence components, which have wavelengths falling within the desired wavelength region, is calculated from the signal intensity of the fluorescence components, which have wavelengths falling within the wavelength region acting as the complementary color with respect to the desired wavelength region, and the signal intensity of the fluorescence components, which have wavelengths falling within the entire measurement wavelength region of the fluorescence. Therefore, the efficiency, with which the fluorescence having been produced from the measuring site is utilized, is capable of being enhanced. Accordingly, adverse effects of noise are capable of being reduced, and the signal-to-noise ratio of the displayed fluorescence image is capable of being kept high.
Also, with the first apparatus for displaying a fluorescence image in accordance with the present invention, wherein the signal intensity of the fluorescence components, which have wavelengths falling within the desired wavelength region, is calculated from the signal intensity of the fluorescence components, which have passed through the all-pass filter for transmitting the fluorescence components having wavelengths falling within the entire measurement wavelength region of the fluorescence, the fluorescence having been produced from the measuring site is capable of being utilized most efficiently, and the signal-to-noise ratio of the displayed fluorescence image is capable of being enhanced even further.
The second apparatus for displaying a fluorescence image in accordance with the present invention is provided with the yellow filter for transmitting only the fluorescence components, which have wavelengths falling within the yellow wavelength region acting as the complementary color with respect to the blue wavelength region, the magenta filter for transmitting only the fluorescence components, which have wavelengths falling within the magenta wavelength region acting as the complementary color with respect to the green wavelength region, and the cyan filter for transmitting only the fluorescence components, which have wavelengths falling within the cyan wavelength region acting as the complementary color with respect to the red wavelength region. Also, the signal intensity of the fluorescence components, which have wavelengths falling within the entire measurement wavelength region of the fluorescence, is calculated from the signal intensity of the fluorescence components, which have passed through the yellow filter, the signal intensity of the fluorescence components, which have passed through the magenta filter, and the signal intensity of the fluorescence components, which have passed through the cyan filter. Thereafter, the signal intensity of the fluorescence components, which have wavelengths falling within the at least one desired wavelength region selected from among the blue wavelength region, the green wavelength region, and the red wavelength region, is calculated from the signal intensity of the fluorescence components, which have passed through the yellow filter, the signal intensity of the fluorescence components, which have passed through the magenta filter, the signal intensity of the fluorescence components, which have passed through the cyan filter, and the signal intensity of the fluorescence components, which have wavelengths falling within the entire measurement wavelength region of the fluorescence. Therefore, the efficiency, with which the fluorescence having been produced from the measuring site is utilized, is capable of being enhanced. Accordingly, adverse effects of noise are capable of being reduced, and the signal-to-noise ratio of the displayed fluorescence image is capable of being kept high. Further, the three kinds of the filters are capable of being utilized also as color filters for acquiring ordinary color images, and therefore the cost of the apparatus for displaying a fluorescence image is capable of being kept low.
With the first apparatus for displaying a fluorescence image in accordance with the present invention, wherein the plurality of the complementary color filters and the plurality of the all-pass filters are arrayed alternately on a two-dimensional plane so as to constitute the mosaic filter, or with the second apparatus for displaying a fluorescence image in accordance with the present invention, wherein the plurality of the yellow filters, the plurality of the magenta filters, and the plurality of the cyan filters are arrayed alternately on a two-dimensional plane so as to constitute the mosaic filter, the signal intensity of the fluorescence components, which have wavelengths falling within the desired wavelength region, is capable of being calculated from the signal intensities of the fluorescence components having wavelengths falling within the respective wavelength regions, which signal intensities have been detected simultaneously. Therefore, the fluorescence image is capable of being displayed in the real time mode, and the reliability of the displayed fluorescence image is capable of being enhanced.